Water-dispersible polysaccharide derivatives of reduced glyoxal content, and a process for decreasing the glyoxal content in glyoxal-crosslinked polysaccharide derivatives
A description is given of glyoxal-treated polysaccharide derivatives which, to decrease the unbound glyoxal, are treated with an aqueous solution of one or more water-soluble aluminium salts, or one or more water-soluble borates, or a combination of one or more water-soluble aluminium salts and one or more water-soluble borates, and, if appropriate, with suitable buffer substances to set the pH, and then dried. A description is likewise given of a process for decreasing the content of unbound glyoxal in glyoxal-treated polysaccharide derivatives.
1. A process for producing glyoxal-treated polysaccharide derivatives comprising:
a) mixing an untreated polysaccharide derivative that is selected from the group consisting of methyl cellulose, methyl hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, methyl ethyl cellulose, methyl ethyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, methyl hydroxyethyl hydroxypropyl cellulose, ethyl hydroxyethyl hydroxypropyl cellulose, methyl carboxymethyl cellulose, ethyl carboxymethyl cellulose, propyl cellulose, isopropyl cellulose, and cyclohexyl cellulose in the form of particles with
i) an aqueous solution of glyoxal,
ii) water-soluble borates in an amount less than 0.5 part by weight per part by weight of glyoxal, and
iii) salts of phosphoric acid as a buffer substance for adjusting the pH value, said mixing being conducted at a temperature of between 20 and 70° C., and
b) drying the resultant mixture, wherein the amount of extractable, unbound glyoxal is less than 0.1% by weight.